JP2000136845A - Active vibration insulating device and exposure device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve vibration eliminating capacity by respectively inserting a displacement generating actuator between a vibration eliminating object and an intermediate plate, inserting an elastic body between the intermediate plate and an installation floor, and driving the displacement generating actuator through a proper compensator after vibration of the vibration eliminating object is detected. SOLUTION: In a vibration eliminating unit used for an electronic microscope and the like, a piezoelectric element 1 is provided as a displacement generating actuator, and for example, a stepper (or a scanner) as a vibration eliminating object is carried on an intermediate plate 5 supported by a plate spring 2 and a laminated rubber 3 through the piezoelectric element 1. In the case of a vibration eliminating operation, a vibration detecting means 8 is provided to detect vibration of the stepper 4, its output is passed a PID compensator 7, and a driving amplifier 9 for applying high voltage on the piezoelectric element 1 by its output is excited. In such constituted active vibration insulating device, it can be built in the vibration eliminating object easily, and thereby, a rise-up time of the vibration eliminating object device can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active vibration isolator used in a semiconductor exposure apparatus for printing a circuit pattern of a reticle on a semiconductor wafer, a liquid crystal substrate manufacturing apparatus, an electron microscope, or the like. More specifically, the present invention relates to an active vibration isolator using a displacement generating actuator such as a piezoelectric element.

[0002]

2. Description of the Related Art In a semiconductor manufacturing apparatus typified by an electron microscope using an electron beam, a stepper, a scanner, or the like,
An XY stage is mounted on the vibration isolator. This anti-vibration device has a function of attenuating vibration by vibration absorbing means such as an air spring, a coil spring, and a vibration-proof rubber. However, in the passive vibration isolator having the vibration absorbing means as described above, even if the vibration transmitted from the floor can be attenuated to some extent, the vibration generated by the XY stage mounted on the same device can be effectively reduced. There is a problem that it cannot be attenuated. That is, the reaction force generated by the high-speed movement of the XY stage itself shakes the vibration isolator, and this vibration significantly impairs the positioning and stabilization of the XY stage.
Further, in the passive vibration isolator, there is a trade-off problem between insulation (vibration isolation) of vibration propagating from the floor and suppression (vibration suppression) performance of vibration generated by high-speed movement of the XY stage itself. In order to solve these problems, in recent years, there is a tendency to use an active vibration isolator. The active anti-vibration device can eliminate the trade-off between vibration isolation and vibration suppression within the range of the adjustable mechanism, and above all, acquire the performance that cannot be achieved with the passive vibration isolator by applying feed forward control positively can do.

[0003] However, in order to further suppress the propagation of vibration to an anti-vibration apparatus such as a semiconductor manufacturing apparatus, it is necessary to perform vibration isolation to a lower frequency range. for that reason,
Attempts have been made to use an active vibration isolator using a piezoelectric element capable of precisely controlling minute displacement for vibration isolation of an entire semiconductor manufacturing apparatus. However, the development of anti-vibration devices using air springs or electromagnetic motors has progressed remarkably to the practical level, whereas active vibration isolation devices using piezoelectric elements as actuators have only been studied at the research level. ing. Regarding the configuration of the control device, there remains a problem that the study is insufficient and the usage of the piezoelectric device is not fully utilized.

FIG. 4 shows a general structure of an active vibration isolator using a piezoelectric element, which is a typical example of a displacement generating type actuator. In the figure, 1 is a piezoelectric element, 2 is a leaf spring,
3 is an elastic body (for example, laminated rubber), 4 is a stepper or scanner to be subjected to vibration isolation, 5 is an intermediate plate, 6
Is the floor. The active vibration isolator having this structure is used based on the idea that a vibration damping target is given and the active vibration isolator shown in FIG. 4 is inserted or laid there. This is because the elastic body 3 inserted between the intermediate plate and the vibration damping target, for example, the laminated rubber, is for alleviating the influence of the unknown dynamics of the vibration damping target 4 on the performance.

However, the dynamics of a semiconductor exposure apparatus that requires an active vibration isolator is not completely unknown, although it is insufficient, and semiconductor device manufacturers who require further vibration isolation using the active vibration isolator have been caught. It is not impossible. Rather, the unknown dynamics are on the floor where the device is installed.

[0006] The floor of a clean room in which industrial equipment such as semiconductor manufacturing equipment is installed has a different vibration mode from place to place even though it is the same floor. In addition, the state of vibration applied to each industrial device differs depending on the number of installed industrial devices installed on the floor and the level of mechanical vibration generated by the same. This phenomenon is natural: the girder and girder supporting the floor,
In addition, the rigidity of the floor is determined according to the natural period of the building itself and the like, and therefore, it is different in distribution.

On the other hand, in consideration of the loading, installation, and start-up steps of the semiconductor manufacturing apparatus, it is desirable that the active vibration isolator itself be built in the semiconductor manufacturing apparatus in advance. However, as mentioned earlier,
The active vibration isolation device is inserted or laid between the semiconductor manufacturing equipment and the floor on which it is installed, and is not incorporated into the semiconductor manufacturing equipment itself as a given function. Did not.

[0008] The principle of the active vibration isolator according to the prior art will be described in more detail. FIG. 4 shows one structure of a vibration isolation unit in which a piezoelectric element is incorporated as a displacement generating actuator. The mechanical model of this structure and the feedback applied thereto are disclosed in Japanese Patent Application Laid-Open No. 8-54039 (rigid actuator active vibration isolator), as shown in FIG. The equation of motion of the system in FIG. 5 is represented by the following equation using the symbols shown.

[0009]

(Equation 1) Here, M _p is the mass of the vibration isolation target, Κ _i is the spring constant of mainly the laminated rubber between the vibration isolation target and the intermediate plate, and C _i is the viscous friction coefficient of the mainly laminated rubber between the vibration isolation target and the intermediate plate. , M _s is the mass of the intermediate plate, K _s is the spring constant of the piezoelectric element, x is the displacement of the vibration isolation target, v is the displacement of the intermediate plate, u is the displacement of the floor vibration, z is the displacement of the piezoelectric element, and s is the displacement of Laplace. Operator. The feedback function is expressed by the following equation.

[0010]

(Equation 2) Here, C _d is a feedback gain of absolute displacement, and C _v is a feedback gain of absolute speed. (1)-
(3) x from the equation, u, when determining the relationship between f _p, the following equation is obtained.

[0011]

(Equation 3)

In the above equation, the mass M is calculated from the displacement u of the floor vibration.
The vibration isolation ratio up to the displacement x of the vibration isolation target of _p is the first term on the right side of the equation (4). The anti-vibration rate in the DC region is given by the following equation when s → 0.

[0013]

(Equation 4)

That is, by adjusting C _d , the vibration isolation ratio at DC can be reduced to 0 [dB] or less. This is a decisive difference from a vibration isolator using an air spring or an electromagnetic actuator. Normally, in an active vibration isolator using an air spring as an actuator, damping is provided by a vibration control loop based on detection of acceleration (absolute acceleration), and a position control loop based on a relative displacement between the floor and the vibration isolator is provided. Is maintaining the specified posture. Due to the feedback of the relative displacement, the vibration isolation rate in the low frequency range is 0
[DB] and will not fall below this value. Equation (6) can be realized only because feedback of the absolute displacement of the gain C _d is performed. That is, the skyhook spring is realized by the feedback of the absolute displacement. The skyhook spring can be realized in principle even with a vibration isolator using an air spring as an actuator, for example. In other words, the characteristics from the input to the servo valve that drives the air spring to the pressure generated by the air spring can be generally regarded as an integral characteristic. Based on this characteristic, the acceleration of the vibration isolation table supported by the air spring is considered. Is detected, and this is negatively fed back to the input of the servo valve through integral compensation. In this way, a skyhook spring can be realized in principle even with a vibration isolation table using an air spring as an actuator. However, in practice, a skyhook spring has been realized in a vibration isolator using a force generating actuator such as an air spring or an electromagnetic motor represented by a linear motor, and there is no example in which the skyhook spring is actually operated. Only by using a piezoelectric element or the like, which is a typical example of a displacement generating actuator, displacement can be precisely controlled, and thus rigidity can be precisely controlled. That is, it is considered that it is practically difficult to realize a skyhook spring using a force generating actuator.

[0015] Next, the response from the disturbance f _p to x (4)
The second term on the right side of the equation, where s → 0, the response in the DC region is expressed by the following equation.

[0016]

(Equation 5) The above equation expresses the compliance of the series spring system. The first term shows the compliance of the hard rubber inserted between the intermediate plate and the vibration isolation target, and the second term shows the compliance of the spring between the piezoelectric element and the intermediate plate and the spring created by feedback.
The second term is the spring K _s between the piezoelectric element and the intermediate plate.
It can be seen that and the spring K _s C _d created by the absolute displacement feedback are connected in parallel. C
_{When d} is increased, the compliance of equation (7) is reduced and the vibration damping characteristics are improved, but the magnitude of the compliance cannot be made smaller than the first term. From the above,
Both equations (6) and (7) are based on a static relational expression.
The effect of _d could be shown explicitly.

Next, the effect of C _v will be described. The function is clear by examining each coefficient relating to the s ² and s terms of the characteristic equation of equation (5), or by referring to the block diagram of FIG. Viscous friction coefficient C _v size K _s C _v by feedback is created. That is, the mechanism is damped to stabilize the mechanism.

[0018]

The active vibration isolator incorporating a piezoelectric element or the like, which is a typical actuator of a displacement type, has already been studied for practical application for application to a semiconductor manufacturing apparatus. However, compared to an active vibration isolator using an air spring or an electromagnetic actuator, a control technique for sufficiently extracting the characteristics of the piezoelectric element has not been established. Moreover, in the conventional active vibration isolator, the structure design and the control device design have been performed from the standpoint that the vibration isolation target is regarded as unknown dynamics. However, from the standpoint of applying the active vibration isolation device to a semiconductor manufacturing device, the unknown dynamics is rather the floor on which the semiconductor manufacturing device is installed.

However, there is no known example of an active vibration isolator which constitutes the structure and feedback of the vibration isolation unit from such a viewpoint, and therefore, has been left as a problem.

An object of the present invention is to provide an active vibration isolator that can further reduce the propagation of floor vibration on which a vibration isolation target is installed and can be built into the vibration isolation target.

[0021]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an object to be isolated, a displacement generating actuator inserted between the object to be isolated and an intermediate plate, and An elastic body inserted between the plate and the floor on which the vibration isolation target is installed, and vibration detection means for detecting the vibration of the vibration isolation target, the output of the vibration detection means via an appropriate compensator The displacement generating actuator is driven based on a signal.

In an active vibration isolator according to a more specific embodiment of the present invention, a vibration damping object is connected to an intermediate plate via a displacement generating actuator, and the intermediate plate and a floor on which the vibration damping object is installed are connected. The vibration detection means detects vibration of the vibration isolation target, and generates a displacement based on a signal obtained by compensating the output of the vibration detection means attached to the vibration isolation target. To drive the shape actuator. Here, when the output of the vibration detecting means is an absolute speed, the compensation applied to the output of the vibration detecting means is a PID compensator. When the vibration detecting means detects the absolute acceleration, an appropriate compensator can be selected in consideration of the dimensions. In addition, the object of vibration isolation is a semiconductor manufacturing apparatus represented by a stepper or a scanner.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a floor on which a vibration damping object is installed is regarded as unknown dynamics. Therefore, an active vibration isolator having a vibration isolating unit obtained by making the structure of the conventional example of FIG. FIG. 1 shows a configuration of an active vibration isolator according to one embodiment of the present invention, and FIG. 2 shows a dynamic model thereof.
As shown, the spring constant K _i, between the floor 6 of the intermediate plate 5 and the floor vibration u of the elastic body 3 is mass M _s of the viscous friction coefficient C _i, the displacement generation actuator 1 generates displacement u _p intermediate It is inserted between the plate 5 and the vibration isolation target 4.

In FIG. 1, for example, a piezoelectric element 1 of a displacement-generating actuator is arranged in the immediate vicinity of a vibration damping object 4. An intermediate plate 5 is provided at the other end of the piezoelectric element 1, and an elastic body of a leaf spring 2 and a laminated rubber 3 is inserted between the intermediate plate 5 and the floor 6. In such an anti-vibration unit, the output of the vibration detecting means 8 for detecting the vibration of the anti-vibration target 4 is passed through the PID compensator 7, and the output excites the drive amplifier 9 for applying a high voltage to the piezoelectric element 1.

Next, the principle will be described. The equations of motion of the active vibration isolator shown in FIGS. 1 and 2 are represented by the following equations using the symbols shown.

[0026]

(Equation 6) Here, the following feedback is applied.

[0027]

(Equation 7) That is, as shown in FIG. 3, the displacement of the piezoelectric element 1 via the PID compensator 7 detects the absolute velocity of the vibration damping subject 4 u _p
Is generated, which is a feedback loop.
From (8) (10), the relationship between the u and f _p to x becomes the following equation.

[0028]

(Equation 8) (11) from the DC (s → 0) vibration transmissibility from floor vibration u to vibration damping subject x in (except Furitsu) x / u and, compliance x from the disturbance f _p to displacement x of the vibration damping target /
f _p is given by the following equations.

[0029]

(Equation 9) In any case, when C _ix is increased, the vibration isolation ratio in the DC region becomes zero.
dB, and compliance can be reduced (stiffness can be increased). In particular, in the active vibration isolator according to the prior art, the compliance can be reduced by increasing C _d as shown in equation (7), but 1 / K _i even in the limit of C _d → infinity.
Can not fall below. However, referring to equation (14), which is a characteristic of the active vibration isolator of the present invention, when C _ix is made infinite, the compliance becomes zero,
That is, the stiffness can be made infinite. Therefore, in principle, the active vibration isolator of the present invention is superior.

Next, the stability of the feedback loop will be described. From equation (12a), K _s C _vx is the effect of mass, from equation (12b), K _s C _xx is the effect of viscous friction,
From equation (12c), K _s C _ix has the effect of rigidity.
It is easy to stabilize the PID by appropriately adjusting the gains (C _xx , C _ix , C _vx ).

The active vibration isolator of the present invention is used to support the entire semiconductor exposure apparatus. Preferably, a semiconductor manufacturing apparatus is provided under an active mount, which is a constituent unit of an active vibration isolator using a conventional air spring or an electromagnetic motor, or in a structural member in contact with the floor of the semiconductor manufacturing apparatus. It has been incorporated.

[0032]

Next, an embodiment of a device production method using the above-described exposure apparatus will be described.
FIG. 6 shows a micro device (a semiconductor chip such as an IC or an LSI,
2 shows a flow of manufacturing a liquid crystal panel, a CCD, a thin-film magnetic head, a micromachine, and the like. In step 1 (circuit design), a device pattern is designed. Step 2 is a process for making a mask on the basis of the designed pattern. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4
The (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 7 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern on the mask is printed and exposed on the wafer by the exposure apparatus having the active vibration isolation device described above. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. Step 19
In (resist removal), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the production method of this embodiment, a highly integrated device, which has conventionally been difficult to produce, can be produced at low cost.

[0035]

The effects of the present invention are as follows. (1) Since the active vibration isolator using the displacement generating type actuator of the present invention can be built in a vibration damping target such as a semiconductor exposure apparatus in advance, the startup time of the vibration damping target device can be reduced. (2) Conventionally, an active vibration isolator using a piezoelectric element, which is a typical example of a displacement-generating actuator, has been designed with a structure and feedback on the assumption that unknown dynamics viewed therefrom are vibration damping targets (for example, a stepper or a scanner). Was. However, the active vibration isolation device of the present invention is designed from the viewpoint that the floor on which the device is installed is regarded as unknown dynamics, not the semiconductor exposure device or the like to be subjected to vibration isolation. Therefore, it is possible to flexibly cope with a vibration environment in which a semiconductor exposure apparatus and the like are installed. (3) According to the active vibration isolation device of the present invention, there is provided, in principle, a structure and a feedback capable of reducing the displacement of the vibration isolation target with respect to disturbance to zero. In the active vibration isolator according to the related art, even if the feedback gain is increased, the compliance is limited to a certain level determined by a spring specific to the mechanism. However, the present invention is free from such a restriction. (4) Therefore, by providing the active vibration isolation device of the present invention, it is possible to reduce the propagation of vibrations of the floor where the object to be isolated, for example, the semiconductor manufacturing device is installed, and thus high accuracy is achieved in the case of the semiconductor manufacturing device. There is an effect that the baking of the IC becomes possible and the yield is improved to contribute to the productivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a vibration isolation unit of an active vibration isolation device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a dynamic model of the active vibration isolator of FIG. 1;

FIG. 3 is a control block diagram of the active vibration isolator of FIG. 1;

FIG. 4 is a diagram illustrating a structural example of a vibration isolation unit of an active vibration isolator according to a conventional example.

FIG. 5 is a diagram showing a configuration of a dynamic model and feedback applied thereto.

FIG. 6 is a diagram showing a flow of manufacturing a micro device.

FIG. 7 is a diagram showing a detailed flow of a wafer process in FIG. 6;

[Explanation of symbols]

1: piezoelectric element, 2: leaf spring, 3: laminated rubber, 4: vibration isolation target, 5: intermediate plate, 6: floor, 7: PID compensator,
8: vibration detection means, 9: drive amplifier.

Claims (5)

[Claims] An object to be isolated, a displacement-generating actuator inserted between the object to be isolated and an intermediate plate, and an elastic body inserted between the intermediate plate and a floor on which the object to be isolated is installed Active vibration, comprising: vibration detection means for detecting the vibration of the vibration isolation target; and driving the displacement generating actuator based on a signal via an appropriate compensator based on an output of the vibration detection means. Insulation device. 2. The output of said vibration detecting means is an absolute speed,
The active vibration isolator according to claim 1, wherein the compensator is a PID compensator. 3. The active vibration isolation device according to claim 1, wherein said vibration isolation target is a semiconductor manufacturing device. 4. An exposure apparatus main body, an intermediate plate supporting the exposure apparatus main body, a displacement generating actuator inserted between the exposure apparatus main body and the intermediate plate, and a floor on which the exposure apparatus main body is installed. An elastic member inserted between the intermediate plate, vibration detection means for detecting vibration of the exposure apparatus main body, and a drive for driving the actuator based on a signal via an appropriate compensator for an output of the vibration detection means An exposure apparatus comprising: 5. A device manufacturing method, comprising manufacturing a device using the exposure apparatus according to claim 4.